Game crash - probably not enoguh memory?

The game keeps crashing after playing for about 5 minutes.
I cannot submit an error log since the windows error also freezes / game logs show nothing special.
But I have to close the process everytime and it shows memory useage of about 95%(xsyon uses about 1.5 gigs of memory).

Can I assume my pc doesnt have enough memory?

I am using windows 7, and I have 2GB DIMM DDR2 800 MHz memory. I have purchased another 2GB and will let you hear if it solved the problem.